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Motion of rotating spherical particles touching a wall
Chára, Zdeněk ; Vlasák, Pavel ; Keita, Ibrahima
The paper deals with an analysis of motion of rotating spherical particle in calm water, when the particle is in contact with a smooth, horizontal wall. The motion was visualized by a fast digital camera at 1000 frames/second. Based on software analysis the particle trajectories as well as rotational velocities were determined. Values of vertical, horizontal and rotational velocities were used as input parameters for numerical model and the results are compared with experimental data. Experiments were performed with glass particle of diameter 25 mm, initial values of rotational speeds varied from 500 to 3000 revolution per minute.
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Influence of the spheroid prolongation on the drag force
Lukerchenko, Nikolay ; Keita, Ibrahima ; Kvurt, Y. ; Miles, Jiří
The drag force acting on a spheroid moving perpendicularly to its axis of rotation in water was studied experimentally. Along the spheroid axis, which is normal to its axis of rotation, a round narrow hole was bored. The spheroid moved along a thin vertical thread stretched in water. A video system recorded the spheroid motion and the spheroid velocity was determined from the record. The drag force coefficient was calculated from the balance of forces acting on the spheroid. Two oblate, two prolate spheroids and one sphere with ratio of the axes 0.67; 0.81; 1.33; 2 and I (sphere), respectively, with approximately the same volumes, were used. The friction coefficient between the thread and spheroid was determined from the comparison of the experimental and calculated motions of the sphere, for which the drag force coefficient is known. The dependence of the drag force coefficient of the spheroid on the ratio of its semi-axes was obtained.
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Experimental evaluation of the drag torque, drag force and Magnus force acting on a rotating prolate spheroid
Lukerchenko, Nikolay ; Keita, Ibrahima ; Kvurt, Y. ; Miles, Jiří
The drag torque, drag force and Magnus force acting on a spheroid rotating around its axis of symmetry and moving perpendicularly to this axis in initially quiescent water were studied using experimental data and numerical simulation. The prolate spheroid with ratio of the axes 4/3 was speeded up in special device, which ensured the required rotational and translational velocity in the given plane. A video system was used to record the spheroid motion in water. Using the video records the spheroid translational and angular velocities and trajectory of its center were determined and compared with the results of the numerical simulation. The dependences of the coefficients of the drag torque, drag force and Magnus force on the Reynolds number and dimensionless angular velocity were obtained.
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